Technical Field
This disclosure relates to service processors, and more particularly, to unlinking devices from a service processor when the device is found to be incorrectly cabled to the service processor.
Description of Related Art
A Service Processor (SP) provides the ability to view and change the power-on settings of a running system. The SP allows connection and management of computing nodes that comprise a multi-node server. Multi node servers typically have cables that interconnect the nodes. For example, an SP could be housed in a control node while there could be multiple nodes housing compute hardware. The SP is connected to the Central Electronic Complex (CEC) hardware via a two way bus Field Replaceable Unit (FRU) Support Interface (FSI) bus. FSI links run in cables that connect the control node to the compute nodes. The control node has specific connector ports into which the interconnect cables are plugged. Each port is designated to connect to a specific compute node. When there are multiple compute nodes, cables can be mis-plugged while either assembling the server or while adding or maintaining nodes.
For example, a port that is supposed to be connected to compute node 1 may mistakenly be connected to node 2. Such mis-cabling cause the SP to access hardware on one node, believing it to be from another node. This leads to RAS (Reliability Availability Service) issues when calling out and identifying the failing hardware. Call-out data may not be collected or controlled via the same mis-plugged interface. Therefore, if allowed to access devices via the mis-plugged FSI, the call-out list would also be incorrect.
Traditional approaches use cable validation algorithms to deal with this problem by validating cables as part of the system initial program load (IPL). Validation of cables is done by providing I/O to provide a cable ID to the nodes. The SP can thus read the identifiers of the node connected at a specific port and compare it against the expected node identifiers for that port. The SP can then determine cable plugging errors and alert the user. However, these algorithms do not prevent the SP from accessing mis-plugged hardware. Consequently, the SP can still access hardware on the mis-plugged nodes and potentially read/write from/to such hardware, running a risk of putting the hardware in a bad state.